The International Astronomical Union Symposium No. 70 on Be and Shell Stars, the Merrill-McLaughlin Memorial Symposium, was held in Bass River (Cap Cod), Massachusetts, U. S. A. , from September 15th through 18th, 1975. Fifty-three astronomers from Argentina, Belgium, Canada, Czechoslovakia, France, Israel, the United Kingdom, the United States, and the Vatican attended and participated in the Symposium. This volume, which parallels the actual program closely, contains the papers presented at the Symposium plus most of the discussion following the papers. New observational techniques and fresh theoretical ideas have resulted over the past few years in a renewed interest in Be and shell stars. At IAU Symposium No. 51 on Extended Atmospheres and Circumstellar Matter in Spectroscopic Binary Sys tems, the Otto Struve Memorial Symposium, in Parksville, British Columbia, Canada, three years ago, a number of participants expressed the wish to organize a symposium on Be and shell stars. If we wish to identify an official 'Father of IAU Symposium No. 70', it would be Mirek Plavec who, in his capacity as President of IAU Commission 42 (Photometric Double Stars) requested and received the cooperation of Commissions 29 (Stellar Spectra) and 36 (Stellar Atmospheres), suggested an Organizing Committee, and wrote to the IAU General Secretary in 1973 requesting that the IAU Executive Committee approve the proposed confer ence as an IAU Symposium.

Inhalt
Introductory Address.- I/Observations of Be Stars.- Spectra and Photometry of Be Stars (Review Paper).- A Survey of H? in the Brighter, Northern Be Stars.- A Study of Be Stars in Clusters.- Emission Features of Several Be Stars as Related to their Luminosity Class and Spectral Type.- Rapid Variations in the Spectra of o And, ? Cas, and ? Oph.- Rapid Variations of H? in Be Stars.- Stellar Photometric Observations at H? through a Narrow-Band Interference Filter.- Spectroscopic Observations of Be Stars in the Near Infrared.- New Observational Data Concerning 4 Her and ? Tau.- The Surface Gravities of Be Stars.- A Comparative Study of the Shell of ? Tau and 48 Lib.- A Model for the Shell of HD 50138.- Observations Récentes de HD 200120.- Singly-Ionized Iron Emission Lines in the Spectra of Early Type Stars.- Pleione as a Variable Star.- Energy Distributions of Be Stars (Review Paper).- II/Be Stars as Rotating Stars.- Be Stars as Rotating Stars: Observations (Review Paper).- Ultraviolet Observations of Rapidly Rotating B-type Stars.- The Relationship of the Oe to the Be Stars.- H? and H? Measures as Related to Be Star Rotation.- III/ New Observational Techniques.- Radio Observations of Be Stars (Review Paper).- Ultraviolet Observations of Be Stars (Review Paper).- A Survey of Mass Loss from Be and Shell Stars, Using Ultraviolet Data from Copernicus.- Ultraviolet Si iv/C iv Ratios for Be Stars.- The Near Ultraviolet Spectrum of ? Tau.- Spectroscopic Observations of the Be Stars ? Cen, ? Cas, and ? Per.- The Far Ultraviolet Spectra of v Cyg and ? Cen.- Photographic Infrared Spectroscopy and Near Infrared Photometry of Be Stars (Review Paper).- Paschen Decrements in Be Stars.- The Classification of Faint Be Stars.- Polarization in Be Stars (Review Paper).-Polarization Measurements Across the Balmer Lines of Be and Shell Stars.- Intrinsic Linear Polarization of Be Stars as a Function of v sin i.- IV/Line Formation in Expanding Atmospheres.- Line Formation in Expanding Atmospheres (Review Paper).- Radiative Transfer in Dynamic Stellar Atmospheres.- Si II Lines in the Shell of ? Tau.- The Complex Structure of the Ca II H and K Lines in the Spectrum of the A0ep Star with Infrared Excess HD 190073.- Theoretical Emission-Line Profiles Computed at Ond?ejov.- Motions in the Shells and Atmospheres of V923 Aql and EW Lac and their Manifestation in the Spectrum.- V/Models.- Models for the Circumstellar Envelopes of Be Stars (Review Paper).- On the Possible Role of Magnetic Fields in the Dynamics of the Be Phenomenon.- Theoretical Wavelength Dependence of Polarization in Early-Type Stars.- The Possible Role of Radiative Acceleration in Supporting Extended Atmospheres in Be Stars.- VI /Single Versus Binary Stars.- Duplicity of Be Stars as Seen from Ond?ejov (Review Paper).- On the Detection of Binary Be Stars.- Evidence for the Existence of Mass-Exchange Binary Be Stars from Periodic Spectral Variations.- Toward a Model for the Be Binary System ? Per.- Final Remarks on the Binary Hypothesis for the Be Stars.- VII/ General Discussion.- General Discussion.- Concluding Remarks.